1. Field of the Disclosure
The present disclosure generally relates to wireless communication. The present disclosure more particularly relates to method of managing E-UTRAN capability of a user equipment.
2. Description of the Related Art
Today, user equipment (UE)'s such as mobile phones, laptops, tablets, and the like and the use thereof have become increasingly popular as communication mediums in a home, office, and/or school environment. Currently, such devices use wireless communication systems with both second generation/third generation (2G/3G) and long term evolution (LTE) capability (fourth generation (4G)) to access data and content. For example, current wireless communication systems include evolved NodeBs (eNodeBs or eNBs) connected to the core network of the wireless communication system. A UE registers with the LTE network for availing evolved packet system (EPS) services from the LTE network. The LTE network is capable of providing both packet switched (PS) and circuit switched (CS) domain related services to the UE. Also, the UE operating in the LTE network can operate in one of the modes including PS mode 1, PS mode 2, PS/CS mode 1 and PS/CS mode 2. For the explanation purpose, the UE operating in PS/CS mode 1 is considered here. The UE operating in PS/CS mode 1 registers with a network for obtaining both EPS and non-EPS services with UE usage setting as “voice centric”. So while accessing CS data, the UE switches to a radio access technology (RAT) with 2G/3G capability if the LTE network is not IP multimedia subsystem (IMS) anchored and while accessing PS data, the UE switches to RAT with evolved universal mobile telecommunication system (UMTS) terrestrial radio access network (E-UTRAN) capability.
However, there are problems/difficulties associated with enabling and disabling of RAT capability as it is based on requirement of the user of the UE. The one or more problems associated with enabling and disabling of the UE's RAT capability with examples are shown in FIGS. 1a to 2c. 
FIGS. 1a and 1b are schematic diagrams illustrating an exemplary problem scenario in which a UE disables a specific RAT capability, according to the related art. As shown in FIG. 1a, consider that the UE 104 is capable of operating in PS/CS mode 1 and can access plurality of radio access technologies such as LTE/UMTS/GSM. The UE 104 sends an attach request message or a tracking area update (TAU) request message to a LTE RAT 108 to avail CS services from a public landline mobile network (PLMN), P1 (102). However, the PLMN P1 (102) is not able to provide CS services to the UE 104 and sends accept message with cause #18 via the LTE RAT 108. The cause #18 indicates that CS services are not available in the current PLMN (P1) 102. Hence, the UE 104 disables E-UTRAN capability and detaches from the LTE RAT. The UE 106 then selects 2G/3G RAT 110 of the PLMN (P1) 102 to avail CS services from the 2G/3G RAT 110. The UE registers with the 2G/3G RAT 110 and initiates a PS/CS session with it.
When the PS/CS session is ongoing, the PLMN P1 102 sends a handover (HO) command to the UE to move to a non-equivalent PLMN, say P2 (120) as shown in FIG. 1b. The UE 106 establishes the PS/CS session with the PLMN P2 120 via 2G/3G RAT 122 of the PLMN P2 120 upon successful HO to the PLMN P2 120. However, even after the PS/CS session is ended in the PLMN P2 120, the UE 104 continues to remain in the 2G/3G RAT 122 even though the PLMN P2 120 is capable of providing CS services over E-UTRAN 130.
FIGS. 2a to 2c are schematic diagrams illustrating another exemplary problem scenario in which a UE disables a specific RAT capability, according to the related art. In this scenario, consider that the UE is capable of accessing plurality of RATs such as LTE, UMTS, and GSM. As shown in FIG. 2a, let us assume that the UE 204 camps on a visited PLMN (VPLMN), V1 (202) and sends an attach/TAU request message to VPLMN (V1) 202. Let us assume that the VPLMN (V1) 202 rejects the UE request message with cause #14 or #15, wherein cause #14 indicates EPS services are not available in the VPLMN and cause #15 says suitable cells for providing CS services are not available in the current tracking area. As a result of this, the UE 204 disables E-UTRAN capability and selects 2G/3G RAT 210 of the VPLMN (V1) 202 to establish a PS/CS session with the network. The UE receives an equivalent PLMN (EPLMN) list including E1 from the VPLMN (V1) 202 upon successful registration with the network. Meanwhile, the PS/CS session is ongoing, the UE receives a HO command to move to EPLMN E1 or UE can reselect to EPLMN (E1) as shown in FIGS. 2b and 2c. However, after the PS/CS session is released, the UE continues to remain in the 2G/3G network 230 even though the EPLMN E1 220 is capable of providing CS services over E-UTRAN 232.
In view of the foregoing, there is a need for a novel method for managing E-UTRAN capability of a UE during the movement to a different PLMN.